In recent years mortality from cirrhosis of the liver has shown a greater increase than death from any other cause; cirrhosis now ranks fourth as the cause of death in men over 40. That one-third of these death occurs as a result of bleeding from varices emphasizes the importance of portal hypertension in the management of patients with advanced cirrhosis. A portacaval anastomosis virtually eliminates variceal hemorrhage but increases mortality from liver failure. This probably occurs because the diversion of portal blood causes a catastrophic fall in total hepatic flow. The static measurements of hepatic blood flow now possibly have proved of little value in the management of portal hypertension but, since the changes are progressive and may fluctuate, we believe it is essential to study the dynamic changes in flow. The course of hemodynamic changes in portal hypertension has not been documented due to the limitations of the techniques available for measuring blood flow. An accurate, totally implantable directional pulsed DOppler ultrasonic flowmeter has been recently developed at Stanford allowing the measurement of blood flow in the portal vein and hepatic artery on multiple occasions over long periods of time. The singular feature of this project is the measurement for the first time, of hepatic blood flow during the induction of chronic liver disease with dimethylnitrosamine and the development of portal hypertension in the dog. These long-term studies over the course of the disease may allow us to characterize the hemodynamic changes and to select the animals most likely to benefit from portacaval anastomosis. Such information may provide a contribution to the management of patients who can benefit from either a shunt procedure or other modes of treatment.